This invention relates to a radar detection system and particularly to such a system utilized in connection with motor vehicle detection systems.
Radar technology has been proposed as a remote sensing solution for future automotive functions such as blind spot detection, adaptive cruise control, parking aid, and collision warning. Such functions may also find applications in connection with other vehicles, such as marine or aircraft. Radar sensor antennas typically emit electromagnetic radiation in a conical or fan-shaped pattern. This pattern defines a xe2x80x9cfield-of-viewxe2x80x9d (FOV) of the sensor. In general, objects outside the sensor""s FOV have a low probability of being detected, and those within the FOV, given they reflect an adequate amount of electromagnetic energy, have a high probability of detection. The vehicle applications mentioned previously may have specified desired detection zones which are not conical or fan-shaped and therefore may not be compatible with the typical radar sensor""s FOV.
The above-referenced problem is particularly significant in connection with certain automotive applications. For example, for use in blind spot detection systems, it is desirable to provide a vehicle operator with a warning of the presence of an obstacle where visual perception is difficult. For such applications, the inability of a radar detection system to properly indicate the presence of an obstacle in a blind spot is a particular concern. Similarly, other applications of radar detection systems often involve critical detection and control requirements.
Various approaches have been considered toward eliminating the previously-mentioned design concerns. One approach to tailoring the radar sensor""s FOV to an irregularly-shaped detection zone is to generate a very narrow beam pattern and then electronically or mechanically scan or sweep the beam over an area of interest. This is the approach used in conventional aircraft detection radar systems in which a narrow beam is swept through an area of interest. The purpose of such rotating or scanning beam in such applications is to provide a high-energy focus beam effective for detection over long distances and further to enable precise positioning information to be obtained from the returned radar signal. Such an approach would enable scanning coupled with appropriate range gating of the return signal to allow the radar sensor FOV to closely match the desired detection zone. However, the creation of a narrow beam pattern requires a physically large antenna aperture and therefore a relatively large package size which may be undesirable in many vehicle applications. Moreover, mechanically or electronically scanned configurations tend to be expensive and can have an adverse effect on overall system reliability.
In accordance with this invention, a radar sensing system and method is provided in which a desired blind spot detection zone is encompassed by at least two radar radiation patterns having differing beam cone angle measures. This plurality of beams can be created using a single radiating antenna which is electronically controlled or by using discrete antennas having differing widths. By comparing the signals, and the signal returns from these plural radiation patterns, appropriate signal processing circuitry can be employed to reveal with a reduced probability of false alarms or missed detections the presence of an object in the detection zone.